Chapter 6

Front 1

Are String objects and reference variables immutable?

Back 1

String objects are immutable, but String reference variables are NOT

Front 2

What must you do after creating a new String to avoid it being lost to your program?

Back 2

You must assign somthing to the new String

Front 3

What happens to the old String if you redirect a String reference to a new String?

Back 3

The old String can be lost

Front 4

String methods use what based indexes?

Back 4

zero-based indexes

Front 5

Only exceptions for zero-based indexes

Back 5

Second argument in substring()

Front 6

Why can't the methods of the String class be overridden?

Back 6

The String class is final

Front 7

length() vs. length

Back 7

• length() is a method Strings have
• length is an attribute arrays have

Front 8

StringBuffer's API vs. StringBuilder's API

Back 8

They're the same, except that StringBuilder's methods are NOT synchronized for thread safety

Front 9

Which methods run faster between StringBuffer and StringBuilder?

Back 9

StringBuilder's methods should run faster

Front 10

True or False? Both StringBuffer and StringBuilder are NOT mutable?

Back 10

False. They are both mutable - they can change without creating a new object

Front 11

String Buffer and StringBuilder methods act on...

Back 11

the invoking object, and objects can change without an explicit assignment in the statement

Front 12

StringBuffer and StringBuilder equals() is NOT overridden, but it doesn't...

Back 12

compare values

Front 13

Chained methods are evaluated from...

Back 13

left to right

Front 14

String method charAt()

Back 14

Returns the character located at the String's specified index. REMEMBER indexes are zero-based

Front 15

String method concat()

Back 15

Returns a String with the value of the String passed in to the method appended to the end of the String used to invoke the method.

The overloaded + and += perform functions similar.

Front 16

String method equalsIgnoreCase()

Back 16

Returns a boolean value depending on whether the value of the String in the argument is the same as the value of the String used to invoke the method.

*Will return true even when characters being compared have differing cases

Front 17

String method length()

Back 17

Returns the number of characters in a String

Front 18

String method replace()

Back 18

Replaces occurrences of a character with a new character.

replace(char old, char new)

Front 19

String method substring()

Back 19

• substring(int begin) Returns a string starting at the location of int begin (zero-based)
• substring(int begin, int end) Returns a string starting at the location of int begin and ends at location of int end (THE 2ND ARGUMENT IS NOT ZERO BASED)

Front 20

String method toLowerCase()

Back 20

Returns a string with uppercase characters converted

Front 21

String method toString()

Back 21

Returns the value of a String

Front 22

String method trim()

Back 22

Returns a String whose value is the string used to invoke the method, but WITH any leading or trailing blank spaces REMOVED

Front 23

StringBuffer method append(String s)

Back 23

Will update the value of the object that invoked the method, whether or not the return is assigned to a variable.

Similar to the + with Strings

Front 24

StringBuilder method delete(int start, int end)

Back 24

Returns a StringBuilder object and updates the value of the StringBuilder object that invoked.

First argument is ZERO-Based

Second argument is ONE-Based

Front 25

StringBuilder method insert(int offset, String s)

Back 25

Returns a StringBuilder object and updates the value of the object that invoked the method.

ZERO-Based argument

Front 26

String vs StringBuffer objects

What will the output be?

StringBuffer sb = new StringBuffer ("abc");

sb.append("def");

System.out.println( sb );

Back 26

"abcdef"

Front 27

StringBuffer method reverse()

Back 27

Reverses the characters in the StringBuffer object

Front 28

StringBuffer method toString()

Back 28

Returns the value of the StringBuffer object that invoked the method call as a String

Front 29

I/O class File

Back 29

An abstract representation of file and directory path names. It's used to work at a higher level, making new empty files, searching for files, deleting files, making directories, and working with paths

Front 30

I/O class FileReader

Back 30

• Read character files with low-level methods
• FileReaders are usually WRAPPED by higher-level objects (like BufferedReader)

Front 31

I/O class BufferedReader

Back 31

• Used to make lower-level Reader classes (FileReader) easier to use
• Compared to FileReaders it reads large chunks of data form a file at once and keeps the data in a buffer
• More convenient methods for reading

Front 32

I/O class FileWriter

Back 32

• Used to write character(s) or Strings to a file
• Usually WRAPPED by higher-level Writer objects (like BufferedWriter)

Front 33

I/O class BufferedWriter

Back 33

• Used to make lower-level classes (FileWriters) easier to use
• Writes larger chunks of data to a file than FileWriters

Front 34

I/O class PrintWriter

Back 34

• Can be used in places where you previously needed a Writer to be wrapped with a FileWriter and/or a BufferedWriter

Front 35

I/O class Console

Back 35

Provides methods to read input from the console and write formatted output to the console

Front 36

True or False? A new File means there's a new file on your hard drive

Back 36

False

Front 37

File objects can represent either a ________ or a ________

Back 37

file

directory

Front 38

The File class lets you do what to files and directories?

Back 38

Manage them (add, rename, and delete)

Front 39

createNewFile() and mkdir()

Back 39

Add entries to your file system

Front 40

FileWriter and FileReader are ______-level I/O classes. You can use them to _________ and ________ files, but they should usually be ________

Back 40

low

read

write

wrapped

Front 41

True or False? Classes in java.io are designed NOT to be "chained" or "wrapped"

Back 41

False

Front 42

What is a common way to get access to higher-level (more convenient) methods?

Back 42

By "wrapping" a BufferedReader around a FileReader or a BufferedWriter around a FileWriter.

Front 43

This Java 5 I/O class has methods append(), format(), and printf()

Back 43

PrintWriters

Front 44

Console objects can read non-echoed input and are instantiated how?

Back 44

Using System.console()

Front 45

Serialization

Back 45

"Save this object and all of its instance variables...unless I've explicitly marked a variable as transient, which means don't include that variable's value as part of the object's serialization

Front 46

The classes you need to understand for Serialization (4)

Back 46

• ObjectOutputStream
• ObjectInputStream
• FileOutputStream
• FileInputStream

Front 47

What must a class do before its objects can be serialized?

Back 47

Implement Serializable

Front 48

ObjectOutputStream.writeObject() method does what?

Back 48

Serializes objects

Front 49

ObjectInputStream.readObject() method does what?

Back 49

Deserializes objects

Front 50

What happens if you mark an instance variable transient? (in regards to serialization)

Back 50

It will NOT be serialized even though the rest of the object's state will be

Front 51

You can supplement a class's automatic serialization process by implementing what methods?

Back 51

writeObject()

readObject()

Front 52

If a superclass implements Serializable then what do its subclasses do?

Back 52

Implements Srializable automatically

Front 53

What happens if a superclass doesn't implement Serializable when a subclass object is deserialized?

Back 53

The superclass constructor will be invoked, along with its superconstructor(s)

Front 54

java.util.Date class

Back 54

Use this class to bridge between Calendar and DateFormat class.

Instance of Date represents a mutable date and time

Front 55

java.util.Calendar class

Back 55

Provides a variety of methods that help you convert and manipulate dates and times

Front 56

java.text.DateFormat class

Back 56

Used to format dates

Various styles like "01/01/70" or "January 1, 1970"

Format dates for numerous locales around the world

Front 57

java.text.NumberFormat class

Back 57

Used to format numbers and currencies for locals around the world

Front 58

java.until.Locale class

Back 58

Used in conjunction with DateFormat and NumberFormat to format dates, numbers and currency for specific locales.

Front 59

How is a Date stored?

Back 59

As a long, the number of milliseconds since January 1, 1970

Front 60

Date objects are go-betweens what two classes?

Back 60

Calendar and Locale

Front 61

What do the methods of Calendar provide?

Back 61

Methods to manipulate dates, getting days of week, or adding some number of months or years to a date

Front 62

How to create Calendar instances?

Back 62

Using static factory methods (getInstance())

Front 63

Calendar method add()

Back 63

Allows you to add or subtract various pieces (minutes, days, years...) to a date

Front 64

Calendar method roll()

Back 64

Works like add() except it doesn't increment a date's bigger pieces. (Adding 10 months to Oct changes the month to Aug but not the year)

Front 65

How to create DateFormat instances?

Back 65

Using static factory methods (getInstance() and getDateInstance())

Front 66

How to create a wide array of outputs for any given date?

Back 66

DateFormat styles can be applied against various Locales

Front 67

DateFormat.format() method is used to create?

Back 67

Strings containing properly formatted dates

Front 68

The Locale class is used in conjunction with which two classes?

Back 68

DateFormat and NumberFormat

Front 69

Both DateFormat and NumberFormat objects can be constructed with?

Back 69

A specific, immutable Locale

Front 70

Regular Expressions (regex) are the patterns...

Back 70

used to search for data within large data structures

Front 71

regex lets you create search patterns using...

Back 71

literal characters or metacharacters (metacharacters allow you to search for slightly more abstract data like "digits" or "whitespace"

Front 72

Searches using Metacharacters /d

Back 72

A digit

Front 73

Searches using Metacharacters /s

Back 73

A whitespace character

Front 74

Searches using Metacharacters /w

Back 74

A word character (letters, digits, or "_" (underscore))

Front 75

Searches using Metacharacters .

Back 75

the "." (dot) means "any character can serve here"

source: "ac abc a c"

pattern: a.c

output

3 abc

7 a c

Front 76

regex provides for quantifiers which allow you to...

Back 76

specify concepts like: "look for one or more thing in a row"

Front 77

Greedy quantifier +

Back 77

Find one or more of the things in a row

source: "1 a12 234b"

pattern: /d+

output

0 1

3 12

6 234

Front 78

Greedy quantifier *

Back 78

Zero or more occurrences

Front 79

Greedy quantifier ?

Back 79

Zero or ONE occurrences

Front 80

How do we fix the problem that metacharacters and Strings don't mix well?

Back 80

We add another backslash in front of the metacharacter

Ex. "//d" instead of "/d"

Front 81

Which classes have Java's most powerful regex capabilities?

Back 81

Pattern and Matcher classes

Front 82

Tokenizing is the process of...

Back 82

splitting delimited data into small pieces

Front 83

How to create a Matcher?

Back 83

Use the Pattern.matcher() method (that takes String sourceData)

Front 84

In tokenizing, the data you want is called_______

Back 84

tokens

Front 85

In tokenizing, the strings that separate the tokens are called.....

Back 85

delimiters

Front 86

How can tokenizing be done? 2 ways

Back 86

With the Scanner class or with String.split()

Front 87

True or False? Delimiters are multiple characters?

Back 87

False. They are single characters like commas, or complex regex expressions

Front 88

What does the Scanner class allow you to do that allows you to stop whenever you want to?

Back 88

Allows you to tokenize the data from within a loop

Front 89

The Scanner class allows you to tokenize these 3 things...

Back 89

• Strings
• streams
• files

Front 90

Why might the String.split() method be slow at processing large amounts of data?

Back 90

It tokenizes the entire source data all at once

Front 91

Two methods used to format data for output. Found int eh PrintStream class, an instance or which is the out in System.out

Back 91

format()

printf()

Front 92

format() and printf() methods are...

Back 92

identical

Front 93

How do you format data with printf() or format()?

Back 93

With FORMATTING STRINGS that are associated with primitive or string arguments

Front 94

format() allows you to mix...

Back 94

literals in with your format strings

Front 95

Format strings values to should know are FLAGS: -,+,0, "," and (

Back 95

• - : Left justify the argument
  
• + : Include a sign (+ or -) with this argument
• 0 : Pad this argument with zeros
• , : Use locale-specific grouping separators
• ( : Enclose negative numbers in parentheses

Front 96

Clue to determining whether you're looking at formatting data...

Back 96

Formatting data will always start with a percent sign (%)

Front 97

Format string values you should know are CONVERSIONS: b, c, d, f and s

Back 97

• b boolean
• c char
• d integer
• f floating point
• s string

Front 98

int i1 = -123

int i2 = 12345

System.out.printf(">%1$(7d< /n", i1);

System.out.printf(">%0, 7d< /n", i2);

Back 98

Output

> (123) <

>012,345<

Front 99

2$ and 1$ in formatting with printf() and format()

Back 99

2$ represents the second argument

1$ represents the first argument

Front 100

What happens if your conversion character doesn't match your argument type?

Back 100

An exception will be thrown